KNOXVILLE, Tenn. (WATE) — Wednesday is the first day of fall and it’s the autumnal equinox. The equinox officially takes place at 3:21 eastern daylight time, but what is an equinox?

It has to do with its alignment of the earth and its position toward the sun. The earth’s axis isn’t straight up and down, it’s tilted by 23.5 degrees. It’s this tilt that gives us our seasons. The tilt of the earth’s axis is toward the sun in the summer and away from the sun in the wintertime. That means that there’s more direct sunlight and longer days in the summertime, and less direct sunlight in the winter.

At the equinox, whether it’s the vernal equinox in spring or the autumnal equinox in the fall, the rays of the sun hit directly on the earth equally because the tilt is neither toward nor away from the sun. It’s parallel. This means that there is an equal amount of daylight and darkness at all latitudes.

As we continue to travel through fall and into the winter, the tilt of the earth goes away from the sun and our days get shorter, nights get longer, and our winters grow colder.